Method and apparatus for efficient production of activated carbon

ABSTRACT

This invention relates to a system for regenerating or manufacturing activated carbon wherein the exhaust gases and vapors from various sections of the furnace are supplied to other sections of the furnace in a recycling manner or are simultaneously cleaned and transformed into fuel gas. In a down-flow embodiment, the water vapor and calorific gasses generated in excess in the drying and devolatilization sections, respectively, are provided, either directly or through a combustion chamber, to the activation section. In an up-flow embodiment, heat from the activation section is recycled to the drying and devolatilization section and the down-flow brings the water vapor from the drying section and volatile material from the devolatilization section into the activation section where it can be effectively used.

FIELD OF THE INVENTION

This invention relates to the regeneration and manufacture of activatedcarbon in a multiple hearth furnace system and utilization of ‘waste’streams from said manufacture to the increase the ultimate efficiencythereof.

BACKGROUND OF THE INVENTION

Activated carbon is a microcrystalline, nongraphitic form of carbonwhich has been processed to increase its porosity. Activated carbon istypically characterized by a large specific surface area, preferably bynot necessarily from 400 to as high as 2500 m²/gram. This large surfacearea enables activated carbons to act as a very effective absorbent as aresult of the high degree of surface reactivity. Favorable pore sizemakes this surface area accessible to gases and liquids. Generally, thelarger the surface area of the activated carbon, the greater is itsadsorption capacity. Activated carbons are used in processes toefficiently remove pollutants from liquid and gaseous streams.

Different kinds of raw materials have been made into activated carbons,including plant material, peat, lignite, soft and hard coals, tars andpitches, asphalt, petroleum residues and carbon black. Coal has beenfound to be a good raw material for the production of activated carbons.

The preparation of activated carbons generally involves two steps.During the first step, noncarbon elements are eliminated as volatilegases by pyrolytic decomposition of the starting material. Where thefeed stock contains water, the first step results in the production ofsteam. Once ‘dry’, a portion of the carbon feed stock is removed throughdevolatilization. As much of the volatile portions of the feed stock aspossible is removed with the goal of only fixed carbon (FC) remainingalong with an unavoidable residue of ash. The ‘pores’ of the remainingcarbon, i.e. the FC, have been exposed by the devolatilization of thefeed stock.

The second step involves a gasification reaction occurring at hightemperature. During this step, the diameter of the pores is enlarged,thus increasing the volume of the pores. Typical reactions taking placein the furnace include the following:

C+H₂O→CO+H₂

C+CO₂→2CO

O₂+H₂→2H₂O

O₂+2CO→2CO₂

CO+H₂O

CO₂+H₂

The H₂O is introduced into the reaction in the form of steam, the C isprimarily the FC resulting from the first step and the remainingreactants are free gaseous molecules.

Gasification converts the carbonized raw material into a form thatcontains the greatest possible number of randomly distributed pores ofvarious shapes and sizes, and a final product with a high surface area.

Besides the activated carbon, outputs of the two steps described aboveinclude steam and volatile matter, both from the first step. It is knownthat steam may be brought from an area of a reaction where it is inexcess to an area where it is required. U.S. Pat. No. 4,455,282 toGerald Marquess and David J. Nell brought waste steam from a drying stepinto the oxidation step, where it was needed for the oxidationreactions.

Besides steam and volatile matter, ‘waste’ outputs from prior artactivated carbon manufacturing include CO₂, H₂ and mixtures of organicvapors and solids of varying sizes. Exhausting these outputs to theatmosphere has become less and less feasible and/or desirable.Segregation of some fractions of such exhaust for recycling, e.g. water,and utilization of realizable chemical energy of other fractions isdesirable for at least this reason.

SUMMARY OF THE INVENTION

A multiple hearth furnace is disclosed wherein a plurality of hearthsare arranged in series. Some of the hearths form a drying sectionproducing water vapor, some form a devolatilization section producingvolatile gas and some define an activation section wherein chemicalreactions take place that consume water vapor and CO₂ and are, as a net,endothermic. Recycled gas from the drying section and devolatilizationsection pass through an outlet attached to an activation section inletby a conduit external to the furnace, whereby the water vapor fractionis consumed in the chemical reactions of the activation section.

The furnace may also include a combustion chamber, in-line with theconduit, whereby the volatile gas fraction of the recycled gas is burnedin the combustion chamber. A water conduit may be attached to thecombustion chamber, whereby supplemental water vapor may be added to thecombustion chamber and heated therein. A portion of the volatile gasfraction may be burned in the activation section.

The multiple hearth furnace may be provided with a recycling fan tooptimize the flow of recycled gas through the conduit. Similarly, anexhaust fan may be connected to the drying section by an exhaust outlet,whereby water vapor and volatile gas not able to be recycled can beremoved from the furnace. A cyclone, or other particulate capture devisemay be used to capture and return fines to the activation zone.

An alternative embodiment of the multiple hearth furnace through which afeed stock containing water, ash, FC and volatile material passes, thefurnace of the alternative embodiment has a similar arrangement ofhearths. A devolatilization section outlet is attached to a conduitexternal to the furnace with a volatile gas valve between thedevolatilization section outlet and the conduit and an activationsection outlet is also attached to the conduit with an activationsection valve between the activation section outlet and the conduit. Theother end of the conduit is connected to a drying section inlet, wherebya controlled portion of the gas inside the furnace flows from the dryingsection, through the devolatilization section and into the activationsection with a portion of the activation section gas anddevolatilization section gas recycled to the drying section.

The alternative embodiment furnace may also have a combustion chamber,in-line with the conduit, between the valves and the drying sectioninlet, whereby a portion of the combustible [the gas contains volatilesand CO, H₂, CH₄ etc] gas fraction of the recycled gas is burned in thecombustion chamber. A recycling fan in-line with the conduit may also beprovided to optimize the flow of recycled gas through the conduit.Similarly, an exhaust fan may be connected to one or more sections byexhaust outlets, whereby gas not needed for recycling is removed fromthe furnace.

The alternative embodiment furnace may be provided with one or moremonitors, e.g. temperature or humidity monitors, supplying data fromwhich it can be determined whether the furnace is performing at anoptimal level. The flow through the activation section valve and thedevolatilization section valve may then be varied independently to alterthe flow therethrough and the flow through the exhaust fan may also bevaried such that the optimal level may be achieved.

Also disclosed is a method and apparatus for recycling and reusing theexhaust gas from an activated carbon producing furnace. The methodincludes utilizing a superheating chamber to heat the exhaust gas to atemperature at which condensable organics are transformed intonon-condensable organics. Water vapor is removed from the exhaust gas,and the exhaust gas is compressed and mixed with a source of oxygen. Theexhaust gas/oxygen source mixture is burned in a gas turbine forgenerating power.

The exhaust gas may be pre-heated prior to the step of superheating theexhaust gas and, since the superheated temperature is no longer needed,the pre-heating step may utilize extraneous heat contained in thesuperheated exhaust gas.

The step of removing water vapor from the gas can be achieved utilizinga condenser and/or a liquid gas separator.

In a preferred embodiment, the oxygen source is compressed atmosphericair.

The ultimate, though not required, goal is a mixture of non-condensableorganics containing a high ratio of ethane and methane.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section of an elevation view of a prior art furnace;

FIG. 2 is a perspective view of a detail showing the rotating shaft andconnected arms with rabble teeth moving over a hearth plate, allcontained in the furnace;

FIG. 3 is a cross-section of an elevation view of an up-flow embodimentof the furnace of the present invention;

FIG. 4 is a cross-section of an elevation view of an alternative up-flowembodiment of the furnace of the present invention;

FIG. 5 is a cross-section of an elevation view of a down-flow embodimentof the furnace of the present invention;

FIG. 6 is a cross-section of an elevation view of an alternativeembodiment of a down-flow furnace of the present invention; and

FIG. 7 is a process flow diagram for a method of cleaning and convertingthe exhaust from a furnace into fuel gas and electrical energy.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, there is shown a multiple hearth furnace 1 ofgenerally cylindrical configuration constructed of a tubular outer steelshell 2, which is lined with heat resistant, insulating material 4. Thisfurnace is provided with a plurality of burner nozzles 6, with one ormore being provided on one or more of the hearths, as necessary, forinitial start-up operation and for controlling the temperatures withinthe different regions of the furnace to carry out the particularprocessing desired. Any suitable type of fuel may be provided to theburners 6.

The feed stock is fed in through an input port 8 and is thereby placedon top hearth 10. The remainder of the moving parts of multiple hearthfurnace 1 serve to transport the feed stock through the hearths,transforming it into activated carbon, which exits the system throughoutlet port 24. The multiple hearths shown in FIG. 1 are divided intothree different major sections. These sections, from top to bottom, aretermed the drying section 26, the devolatilizatoin section 28 and theactivation section 30. In the present example, the drying section 26comprises hearths 10 through 13. The devolatilization section compriseshearths 14 through 17, which vaporize the volatile portion of the feedstock, leaving inert ashes and fixed carbon (“FC”). The FC and ash thenpasses to the activation section 30, comprising hearths 18-20 and exitsoutlet port 24.

From feed stock to activated carbon, as well as the intermediate andwaste materials, the solids are moved through furnace 1 through acombination of gravity and pushing. The pushing is accomplishedutilizing arms 32 mounted on a rotating central shaft 34. Each arm 32contains a plurality of rabble teeth 36. During operation, the centralshaft 34 rotates and the arms 32 move around the hearth. The rabbleteeth 36 are angled with respect to the rabble arms 32 and positioned onthe rabble arms 32 so as to result in a net advance of the solids in aradial direction. In FIG. 2, toward the opening 40 at the center of thehearth bed 38 where it falls to the next hearth below. As can be seen inFIG. 1, the hearths alternate between central openings 40 and peripheralopenings 42. Likewise the angle of the rabble teeth 36 alternate fromone set of arms to the next such that they are always pushing the solidstoward the hearth opening 40 or 42. To improve solid phase mixing andincrease the time the solids reside on a hearth, one of the four rabblearms may be fitted with rabble teeth having the reverse angle (backrabble arm) causing the solids to be moved away from the hearthdischarge by this one arm.

Thus, the feed stock to be processed enters the top of the furnace at aninlet 8 and passes downwardly through the furnace in a generallyserpentine fashion alternately inwardly and outwardly across the hearthsand is discharged at the bottom of the furnace, as indicated at 24.

Exhaust gases from the furnace are discharged from an outlet 44 at thetop of the furnace 1. In the prior art, in order to support combustion,air was added at the bottom of the furnace. Additional air was added, asdeemed necessary, in various other hearths throughout the furnace. Anexhaust fan 46 could be fitted to encourage the upward flow through thefurnace 1. The upward flow of hot gas can be some portion, or all, ofthe heat needed to dry the feed stock in drying section 26. The exhaustgases discharged through outlet 44 are, thus, removing the water vaporfrom the drying section 26.

Once dried, the material is heated to about 1400° F. in thedevolatilization section. The specific solids temperature required is afunction of the feed material. All of the volatile material passes fromthe solids into the atmosphere inside the furnace 1. Only FC and ashremain. The FC moves into the activation section. In the activationsection, the key chemical reactions are:

C+H₂O→CO+H₂(endothermic)

C+CO₂→2CO(endothermic)

O₂+H₂→2H₂O(exothermic)

O₂+2CO→2CO₂(exothermic)

CO+H₂

CO₂+H₂(reversible)

Note that there is no burning of the volatile material. This material isnot present in the activation section 30 in the prior art, up flowdesign, it having flowed away from the activation section 30 and intothe drying section 26 and out the exhaust outlet 44.

FIG. 3 shows furnace 1 having a second exhaust outlet 48. Some portionor all of the exhaust from drying section 26, including a substantialportion of steam from the drying process, may exit outlet 48 and beconveyed by pipe 50 as a recycle stream into the activation section 30.The water fraction supplies some or all of the H₂O for the abovedetailed chemical reactions necessary for activation of the FC.

In addition, the vaporized volatile matter in this recycle stream,having flowed from the devolatilization section 28 into the dryingsection 26, is fuel. The vaporized volatile matter fraction of therecycle stream is injected into the gas space above the FC material inthe activation section 30 and all or a portion is burned as fuel. Thus,the exhaust gas from drying section 26 and devolatilization section 28are recycled and used as a source of free steam and fuel to add energyfor the endothermic reactions of activation. A significant portion ofthe fuel used to create steam to be injected into the activation section30 will be saved by use of the recycled steam. In addition, asignificant portion of the fuel used to support the endothermicreactions in the activation section 30 will be replaced by the recycledfuel. Recycling fan 52, or other means, may be used to regulate flow ofthe recycle stream into the activation section 30.

FIG. 4 shows a combustion chamber 54 outside of the shell 2 of thefurnace 1. Inputs to the furnace may include the recycle steam from thedrying section 26 and devolatilization section 28, as well assupplemental air from air line 56. The air is supplied to combustionchamber 54 through air line 56 and water is supplied through pipe 58.These supplements may be necessary to optimize the desired levels inactivation section 30, particularly of water. In the event that too muchsteam is entering activation section 30, a greater proportion of exhaustfrom the drying section 26 may be passed through outlet 44 instead ofbeing recycled.

Besides optimizing the steam concentration, combustion chamber 54 may beused to optimize burning of the fuel fraction of the recycled gasstream. The fuel fraction of the recycled gas stream contains thevolatiles as well as H₂ and CO from various chemical reactions withinthe furnace 1, particularly from the activation section 30.

FIG. 5 discloses an alternative embodiment of furnace 1 wherein the flowof gasses is down, i.e. a down flow furnace. Note that the exhaust gasleaves the furnace at hearth 20, as opposed to hearth 10 in the up flowembodiments of FIGS. 1, 3 and 4, discussed above. One advantage of thedown flow is most of the volatiles from the devolatilizing section 28,instead of heading toward the drying section 26, flow toward theactivation section 30 and are either burned or converted tonon-condensable gases such as N₂, CO₂, CO, H₂CH₄, for example.

Available down flow furnaces provide the heat required for the dryingsection 26 and devolatilizing section 28 either with fuel burners or byrecycling hot gas from the hearths 18-20 of the activation section 30into the drying 26 and devolatilization 28 sections. Furnace 1 of FIG. 5takes the gases from hearths 18-20 through outlets 60, 62 and pipe 64,recycling that gas to top hearth 10. In addition, gas may be recycledfrom one of the devolatilization hearths 14-17 through outlet 68. Flowsfrom outlets 60, 62 and 68 may be adjusted through valves 66 adjacenteach outlet.

As in FIG. 3, recycle pipe 64 may be directly attached (not shown) totop hearth 10 inlet 70 with a recycle fan 54, as necessary, providingthe energy needed for drying and devolatilization, with the availablevolatiles burning in the furnace 1 and adding their energy where needed.As in FIG. 4, a combustion chamber 54 may be provided outside of furnace1. The gasses from activation section 30 and devolatilization section 28are fed into combustion chamber 54 along with supplemental air from airline 56 and supplemental water from water pipe 58, as necessary. Aportion of the volatiles and any other calorific gas from outlets 60, 62and 64 are burned prior to being added to top hearth 10 through inlet70. Gas not needed for recycling is drawn off at outlet 72 by exhaustgas fan 46. Excess combustible gas is allowed to flow down through thedrying and devolatilizing zones. Injection air is used in the hearth'sgas spaces in the drying and devolatilizing zones to burn a portion ofsuch gas as a heat source.

Actuatable valves 66 and the power to exhaust fan 46 are controlled suchthat the composition of the recycled gas passing through recycled gasfan 52 is controlled for multiple variables. That is, the fuel content(primarily derived from outlet 68 of devolatilization section 28) andthe steam content (primarily derived from outlets 60, 62 of activationsection 30) of the recycled gas are monitored and controlled byadjusting the flow through outlets 60, 62 and 68 by valves 66 and theexhaust flow through outlet 72 by the power supplied to exhaust gas fan46. FIG. 6 discloses an alternative embodiment for situations where thefeed stock may be excessively high in volatiles. In such a case there isthe possibility that drawing too many volatiles through activationsection 30, with or without the volatiles through outlet 68 and recyclepipe 64, may cause a decrease in activation rate. The excessivevolatiles may be controlled with an outlet 74 in one of thedevolatilization hearths 14-17 attached to outlet fan 46. Valves 66 mayalso be added in line with outlet 74, as well as in line with outlet 72,to meter the gases drawn from the devolatilizing section 28 and theactivation section 30.

Standard temperature, humidity, sampling and/or otherwise appropriatemonitors may be located at any convenient location of any of theembodiments described herein. Data from these monitors may be used tooptimize the drying, devolatilization and activation processes occurringin furnace 1. Such optimization may take the form of adjusting valves 66to vary gas flows to/from various sections of the furnace as well asadjusting the power supplied to either of fans 46 or 52, particularlywhere the inlets to fans 46, 52 are not provided with a valve.

It is also possible to use raw materials such as old tires that aresuitable for the manufacture of activated carbon, but which arrive voidof water. In this embodiment, although the water can still be insertedinto the process to generate the required steam, the energy to heat suchwater can still be derived from the process as explained above.

It is also noted that in an arrangement like that shown in FIG. 5, wheregas from the devolatilization section and from the bottom hearth aremixed, some minor empirical experimentation may be needed to optimizethe process. Specifically, increasing the flow from the devolitilizationzone reduces the combustible material flowing to the activation zone.This reduces the heat available by burning this gas with injection air.It also reduces the chance of the product being contaminated byadsorbing impurities. Taking more from the bottom flue draws more waterand more combustible material to the activation zone. The balance is torecycle enough to get high water and low combustible into the activationzone, which balance can be arrived at in any particular system by simplyaltering the amount taken from each zone.

To one degree or another, the preceding methods and apparatus may haveone or more outputs that are not useful (e.g. activated FC), immediatelyrecycled (e.g. water vapor mixed with vaporized volatile matter) orharmless (e.g. pure water/water vapor). To an ever increasing degreedepending upon the industrial application and geographic/jurisdictionallocation of the apparatus in question, simply exhausting anything butthe purest and most benign byproduct of the present method and apparatusto the atmosphere is no longer an option. Even emissions of CO₂,formerly considered almost as benign as pure H₂O or air, is coming underincreasing scrutiny.

Certainly, liquid H₂O or air/H₂O vapor mixed with CO₂, H₂ and mixturesof organic vapors and solids of varying sizes can be problematic todiscard or recycle. The preceding embodiments sought to reuse andrecycle these emissions to the greatest degree possible. FIG. 7 shows anapparatus and method for handling outputs treated as ‘waste’ in theprior art in such a way as to minimize the volume of ‘waste’, especiallythe volume of more pernicious components thereof. As much of the wasteas possible from furnace 1 is transformed into components that can beimmediately reused; such reuse will most preferably involve furnace 1,its proximity to the apparatus of FIG. 7 being established. That is, thewaste is cleaned and transformed into power. The apparatus of FIG. 7 isreferred to hereinafter as the FGC&PG 80; FGC&PG is an acronym for FuelGas Cleaning & Power Generation.

FGC&PG 80 is attached to the multiple hearth furnace 1 described abovewith only relevant outputs shown in FIG. 7, i.e. dust collector 81 andemergency by-pass stack 82. The emergency by-pass stack 82 provides avent for material utilized in the FGC&PG 80 in the event this apparatusneeds to be taken off-line. Dust collector 81 receives exhaust fromfurnace 1 and extracts dust particles from this exhaust. These dustparticles may be returned to furnace 1. In a preferred embodiment, dustcollector 81 is a cyclonic type known in the art and may act as or beintegral with a fan 46 to the extent increased flow from furnace 1 intoFGC&PG 80 might be necessary. FGC&PG 80 may receive exhaust from any ofthe drying hearths 10-13, devolatilization hearths 14-17 or activationhearths 18-20 of furnace 1; exhaust from two or even all three hearthtypes may comprise a mixed input to FGC&PG 80. Theconfiguration/operating parameters of furnace 1 and theconfiguration/operating parameters of FGC&PG 80 will determine themixing ratios, which may be adjusted with valves 66.

Gas exits dust collector 81 and is conveyed to heat exchanger 86 throughconduit 84. The gas in conduit 84 contains relatively large fractions ofwater vapor, organics, carbon dioxide, hydrogen, carbon monoxide, tarand other particulates. The temperature of the gas in conduit 84 is ofthe order of about 950° F. The gas gains energy in heat exchanger 86,exiting with a temperature of about 1900° F.

From heat exchanger 86, the gas is conveyed to superheat chamber 90. Airis added to the gas to promote combustion and the temperature of themixture is raised to approximately 2100° F. by combustion in thesuperheater. The purpose of the superheat chamber is to raise thetemperature of the gas high enough to cause larger particles and largemolecular weight organic molecules to decompose to smaller organics,with ethane (C₂H₆) and methane (CH₄) being the ultimate, though notrequired, goal.

The high temperature of the gas exiting the super-heater 90 is notnecessary for later steps and may, therefore, be used for the source ofheat for heat exchanger 86. The superheated gas enters the top of heatexchanger 86 and is used to raise the temperature, as mentionedpreviously, of the gas from conduit 84. Thus, the now extraneously hotgas from superheater 90 is used to preheat the gas going into thesuperheater 90 to minimize the amount of energy that needs to beexpended in superheater 90 to raise the gas to the decompositiontemperature.

The gas exiting heat exchanger 86 will be a slightly hotter than the gasentering the heat exchanger 86 from conduit 84, e.g. approximately 1200°F. This gas still contains large fractions of water vapor, carbonmonoxide and hydrogen, but as much of the organics/tar as possible willhave been decomposed into non-condensable, smaller molecule organics.This gas is passed through a condenser 96 in which it is cooled, e.g. byair or water, down to approximately 110° F. Water exits the condenser 96through conduit 104, after cleaning, this water can be used in otherapparatus needing water, e.g. furnace 1. The remaining gas is conveyedto liquid gas separator 102 to separate as much of the remainingcondensed water vapor as possible; from whence it is added to conduit104. The gas may now, most accurately for this FGC&PG 80 apparatus, beconsidered fuel gas. After a final pass through particulate controlfilter 108, from which dust particles are removed through conduit 110,the gas enters compressor 112. Compressed fuel gas exits compressor 112at a pressure appropriate for a gas turbine 116, e.g. 500 psi.Atmospheric air may be utilized as an oxygen source for the gas turbine116. Air is supplied to compressor 106 from the atmosphere through line100. The pressurized air and fuel gas are combined and ignited in thecombustor 114 element of gas turbine 116. The result of this combustionprocess is a great increase in the volume and temperature of the fuelgas/air combination. This combustion product is the input to the bladesof gas turbine 116, causing the blades to be displaced and exert torqueon shaft 118. Shaft 118 may be attached to AC generator 118, resultingin the generation of AC power.

Thus, FGC&PG 80 reduces a potentially problematic gaseous mixture ofair, H₂O, CO₂, H₂, CO, organics and solid particulates of varying sizesto pure water, collected dust, electrical energy and emissions from gasturbine 116. The water can be utilized in any number of ways, includingin multiple hearth furnace 1 for production of activated carbon.Although CO₂ is, ultimately, exhausted from FGC&PG 80 as exhaust fromgas turbine 116, the overall energy system emits a lower ratio CO₂ toKWh than burning coal directly to energy. The improvement being afraction of the carbon present in the original coal is removed from theprocess as activated carbon. In addition, the relative purity of thecompressed fuel gas entering combustor 114, i.e. in contrast to burningpure coal, results in minimal less desirable emissions from turbine 116.

The temperatures provided in the description of FGC&PG 80 are exemplary.The actual temperatures will be partially dependent upon the temperatureof the gas in conduit 84, which will be fixed by the temperatures invarious zones of furnace 1 and the ratio of exhaust from each zone; andpartially dependent upon the temperature needed in superheat chamber toefficiently decompose molecules and particles.

Although certain particular embodiments of the invention are hereindisclosed for purposes of explanation, various modifications thereof,after study of this specification, will be apparent to those skilled inthe art to which the invention pertains.

It is noted that, while the invention has been described with referenceto various embodiments, it is understood that the words which have beenused herein are words of description and illustration, rather than wordsof limitation. Further, although the invention has been described hereinwith reference to particular means, materials and embodiments, theinvention is not intended to be limited to the particulars disclosedherein; rather, the invention extends to all functionally equivalentstructures, methods and uses, such as are within the scope of theappended claims.

Those skilled in the art, having the benefit of the teachings of thisspecification, may achieve numerous modifications thereto and changesmay be made without departing from the scope and spirit of the inventionin its aspects.

1. A fuel gas cleaning and power generation method, comprising the stepsof: a. acquiring a gas from one or more exhausts of a furnace utilizedin transforming a carbon source into activated carbon; b. heating thegas in a superheat chamber to a decomposition temperature sufficient tocause the condensable organics to decompose toward non-condensableorganics; c. separating H₂O from the gas; and d. combusting the gas toprovide energy.
 2. The fuel gas cleaning and power generation method ofclaim 1, further comprising the steps of: a. mixing the gas with anoxygen source; and b. utilizing the combustion energy to turn the shaftof an electrical generator.
 3. The fuel gas cleaning and powergeneration method of claim 2, further comprising the step of: a.compressing the oxygen source and gas.
 4. The fuel gas cleaning andpower generation method of claim 1, further comprising the step of: a.pre-heating the gas prior to the step of heating the gas in thesuperheat chamber.
 5. The fuel gas cleaning and power generation methodof claim 1, further comprising the step of: a. removing particulatematter from the gas.
 6. The fuel gas cleaning and power generationmethod of claim 1, wherein the step of separating H₂O from the gasincludes a condenser and liquid gas separator.
 7. The fuel gas cleaningand power generation method of claim 1, wherein the non-condensableorganics are ethane and methane.
 8. A method of transforming exhaustfrom a furnace being utilized to manufacture activated carbon, theexhaust being a gas containing condensable organics and water vapor,into fuel gas and electrical energy, comprising the steps of: a. ventingthe gas from the furnace; b. heating the gas to a temperature sufficientto cause the condensable organics to decompose toward non-condensableorganics; c. separating H₂O from the gas; d. compressing the gas; e.mixing the gas with an oxygen source; f. combusting the gas and oxygenmixture; and g. utilizing the combustion energy to turn the shaft of anelectrical generator.
 9. The method of claim 8, further comprising thestep of: a. pre-heating the gas prior to the step of heating the gas.10. The method of claim 8, further comprising the step of: a. removingparticulate matter from the gas.
 11. The method of claim 8, wherein thestep of separating H₂O from the gas includes a condenser and liquid gasseparator.
 12. The method of claim 8, wherein the oxygen source iscompressed atmospheric air.
 13. The method of claim 8, wherein thenon-condensable organics are ethane and methane.
 14. A method forrecycling and reusing a stream of exhaust gas from a furnace producingactivated carbon comprising the steps of heating the exhaust gas to atemperature at which condensable organics are eliminated andnon-condensable organics are created, removing water vapor from theexhaust gas, compressing the exhaust gas, mixing the exhaust gas with asource of oxygen, utilizing the exhaust gas/oxygen source mixture asfuel for a gas turbine and generating power with the gas turbine. 15.The method of claim 14, further comprising the step of pre-heating theexhaust gas prior to the step of heating the exhaust gas.
 16. The methodof claim 15, further wherein the pre-heating step utilizes extraneousheat contained in the exhaust gas subsequent to the heating step. 17.The method of claim 14, wherein the step of removing water vapor fromthe gas includes a condenser and liquid gas separator.
 18. The method ofclaim 14, wherein the oxygen source is compressed atmospheric air. 19.The method of claim 14, wherein the non-condensable organics are ethaneand methane.